SABANA CRESPO, Colombia  Coca leaves, the raw material of cocaine, should speed you up and give you a buzz. But you'd never know it to look at the Arhuaco Indians of Colombia's Sierra Nevada, who must be strong contenders for the title of World's Most Laid-Back People.

Cistercian monks would make more of a racket in deep contemplation than two Arhuaco men when they meet. They grin and whisper a few words in their soft-sounding language, dipping their fingers into little cloth bags to make the ritual greeting of exchanging coca leaf.

Male Arhuacos chew coca almost all the time, their cheeks permanently bulging with darkening green cud.

Yet, despite the stimulant, they pad around in sandals and flowing white robes in as quiet and unhurried a way as if the last few hundred years of frenetic human development had never happened.

Which is exactly how they would have liked it.

At a meeting in late September, advised by coca-chewing shamans, or mamos,,/i> the Arhuacos decided to tell the "white" civilization of the rest of Colombia to leave them alone in their ancestral home in the Sierra Nevada mountains.

"As of today, we won't permit the construction of any new roads because they destroy sacred sites," said Jeremias Torres, a senior member of the council representing the 20,000 Arhuacos.

He spoke in Sabana Crespo village, a collection of simple cabins in the foothills of the Sierra Nevada, the world's tallest coastal mountain range whose snowy peaks rise above the steamy jungles of Colombia's Caribbean shore.

"The things we need here already exist. Like the water, like the air, like the soil and the sun which shines on us," said Torres as he chewed.

Unfortunately for the Arhuacos, while Colombia's 1991 constitution concedes a degree of Indian self-government on traditional lands, it gives them very little power to stop infrastructure projects.

A lawyer from the Colectivo de Abogados who works on human rights cases, Reinaldo Villalba, said their best hope would be to mobilize international opinion.

But the Arhuacos are suspicious of outsiders, particularly journalists. Torres only spoke to a reporter after a ruminative assembly in a thatched mud hut granted approval.

"We're not going to permit electricity either," said Torres.

Asked about a telephone tower in the tiny village he replied sharply: "We're going to get rid of it. We don't want it any more."

Anger at Dam Plans

A crowd listened while he spoke.

The men wore white caps the shape of flattened ice cream cones and steadily rubbed and poked ritual gourds with sticks, a movement which has religious significance and represents the conjunction of male and female. The women were bare headed and carried silent babies bound in blankets to their backs.

They are particularly angry about government plans to build the Besotes Dam on the Guatapuri River for the water supply of the city of Valledupar.

"It pains us to think they could tap the rivers because our spirits travel through them when we die. We don't want our spirits to get stuck in the public water pipes," said Torres.

But while the regional government is moving forward with plans for Besotes, cultural disintegration is not the Arhuacos' only fear. They have an enemy no court has been able to control and which pays no attention to international opinion.

Outlaw far-right militias have targeted them in their push for control of the strategically important Sierra Nevada. Coca plantations, which, unlike those belonging to the Indians, are illegal and used to make cocaine, are now hidden in the mountains' jungle-covered folds.

"They killed two Indians near here. They cut them up into pieces," said Torres.

After the killings late last year, the paramilitaries said they had made a mistake and had been misinformed that the Indians were helping Marxist rebels, who are fighting a 40-year-old war.

But, Torres said, "There is no pardon for what they did."

The Colombian government is negotiating peace with the paramilitaries, although it accuses them of regularly violating a cease-fire. While members of the army have often cooperated with the "paras" against their common rebel foe, the military does pursue them when caught law-breaking.

But the Arhuacos are very exposed in their mountain villages.

"We have been facing the situation with words. We repeat our position that this is our land and we govern ourselves, and we ask for respect, although we have received very little," Torres said, adding that the paramilitaries don't let the Indians bring food into the Sierra Nevada, in case it ends up feeding rebels.

Nonetheless, the Arhuacos are determined to face off both the juggernaut of Western civilization and the guns of the paramilitaries. They don't want tourists gawking at them or anthropologists studying them. And they don't want to change the way they think.

"According to European histories, we crossed the Bering Straits and came here via the Polynesian Islands, and we don't accept that. We were born here, together with the stones, the soil, and the air," said Torres.